A glass bowl is a necessary piece of equipment if a bong is your go-to choice for smoking flowers. Glass bowls for bongs typically are made out of high-quality glass and come in different sizes and colors. Generally, the glass bowl is a borosilicate compound that is made for being strong and durable. The two most common sizes of bowls are 14 mm and 18 mm bowls though other sizings exist. Before buying a glass bowl, make sure your bong slide is the right size to fit the bowl. Nothing is worse than picking out a good glass bowl only to find out it won’t fit on your rig.